Pterygium is an ocular disease which is characterized by the encroachment of a fleshly and congestively triangular portion of the bulbar conjunctiva onto the cornea and caused by external stimuli such as ultraviolet light, dry atmosphere, heat, cold and dust. In particular, pterygium has been largely observed on the cornea at the nasal side along the palpebral fissure. Pterygium progresses gradually toward the top of the cornea from the conjunctiva and reaches the pupillary area to cause visual loss. At the present time, there is no therapeutic agent which can inhibit or which is effective against the progress of pterygium. Therefore, development of an effective therapeutic agent against this disease has been desired. Accordingly, pterygium treatment, has involved only surgical operations such as to remove pterygium tissues.
Unfortunately pterygium surgery, there is a high incidence of recurrence of pterygium, about 30-50%, which remains a serious problem. Therefore, in the field of the pterygium medication, earnest studies have been actively promoted in order to find substances which are effective for inhibiting the recurrence of pterygium. Up to this time, for example, it was confirmed that anti-tumor agents such as mitomycin were effective. However, concern regarding theses drugs have been raised relative to the incidence of serious side effects such as scleromalacia [Connective Tissue, Vol.26, pp135-137 (1994) etc.]. In view of said concerns, such drugs have not been sufficiently tested enough to use clinically. In addition, it has been reported that beta-ray radiation using strontium 90 was effective in inhibiting postoperative recurrence of pterygium. However, injuries such as cataract formation have been noted [Ganka, Vol.24, pp917-923 (1982) etc.].
On the other hand, tranilast has been widely used as a drug for the treatment of allergic disorders such as bronchial asthma, allergic rhinitis, atopic dermatitis and allergic conjunctivitis, and cutaneous disorders such as keloid and hypertrophic scaring. For example, it has been known that tranilast has inhibitory activities on chemical mediator release caused by an allergic reaction, excessive collagen accumulation by fibroblast cells in cutaneous tissues and excessive proliferation of smooth muscle cells in coronary artery vessels.
However, it has not been disclosed that tranilast has an inhibitory activity on progress of pterygium and postoperative recurrence of the same and it is not known that tranilast is useful as an agent for inhibiting the progress of pterygium and postoperative recurrence of the same.